You are getting pre-owned equipment, so it would be a little bit difficult to generalise: a Rolleiflex might have a better reputation than a "Something-flex" made in somewhere else, but if the Rolleiflex had been trashed by a previous owner, its lenses no longer properly synchronised in focal length, etc, it might not be any more satisfactory than the latter.

If you see one at a dealer, try to arrange for a money-back guarantee: that's what I always do:

Seal your cash in an envelope with your contact details etc, and get the shop manager to sign it as well, let him put it in the cash register, the deal is this: if you do not return with the camera within 24 hours, he can open up the envelope and put the money away; but if you return with the camera, you can take the sealed envelope back. You take pictures with it for the day and get them processed and carefully examined, whether it works or not, you still won't be out of pocket.

I have done arrangements with dealers like that and it seems quite acceptable to every one of them; it is perhaps worth a try.